Amyotrophic lateral sclerosis (ALS) with demyelinating polyneuropathy is a rare condition. We describe two ALS patients with demyelinating neuropathy. Immunomodulatory therapies brought slight symptomatic benefits to the patients, but the treatments could not halt the progression of ALS. Chance coincidence of the two diseases is unlikely in view of the low prevalence. ALS, mainly consisting of progressive axonal degeneration, might show temporal demyelinating features of peripheral nerves both electrophysiologically and pathologically. The pathomechanism for the demyelination in ALS remains to be elucidated.